package example;

import java.util.Random;

public class VerificationCode {
    public static void main(String[] args) {
        String str = generraterVercode(4);
        System.out.println(str);
    }
    public static String generraterVercode(int len){
        String code = "";
        Random rand = new Random();
        char[] chs = {'a','b','c','d','e','f','g','h','i','j','k','l','m','n',
                'o','p','q','r','s','t','u','v','w','x','y','z',
                'A','B','C','D','E','F','G','H','I','J','K','L','M','N',
                'O','P','Q','R','S','T','U','V','W','X','Y','Z',
                '0','1','2','3','4','5','6','7','8','9'};
        for (int i = 1;i<=len;i++){
            int index = rand.nextInt(chs.length);//0-61
            code+=chs[index];
        }
        return code;
    }
}
